Man-made consolidated cellulosic articles, such as fiberboard, hardboard, medium density fiberboard, and the like can be press molded or embossed to have three-dimensional shapes and/or various design and structural features found in natural wood. Types of useful consolidated cellulosic articles are referred to by terms such as: (a) fiberboards, such as hardboard (e.g., low-density or high-density hardboard), soft board, medium-density fiberboard (MDF), and high-density fiberboard (HDF); and (b) chipboards, such as particleboard, medium-density particleboard, and oriented strandboard (OSB). Such composite articles can be used as columns, floors, floor underlayment, roof sheathings, ceilings, walls, wall coverings, wainscots, partition systems, doors, door skins, and stairs in the construction of homes, offices, and other types of buildings, as well as furniture components, such as chairs, tables, countertops, cabinets, and cabinet doors, and other uses, such as bulletin boards, for example.
Various processes can be used to produce consolidated cellulosic articles, including wet-felted/wet press or “wet processes”; dry-felted/dry-pressed or “dry” processes; and wet-felted/dry-pressed or “wet-dry” processes. Such processes are discussed in further detail in U.S. Pat. No. 6,524,504, the disclosure of which is incorporated herein by reference. The disclosed invention is preferably implemented through use of a dry process in order to minimize environmental impact.
Conventionally, consolidated cellulosic articles typically include a formaldehyde-based binder, such as phenol formaldehyde or urea formaldehyde, to “glue” the cellulosic fibers together. Formaldehyde binders are low cost and compatible with the hydrophilic nature of cellulosic fiber, readily reacting with the high population of hydroxyl groups of cellulose, hemi-cellulose, and lignin components of the fiber to bind the fibers together.
Wood fibers used to make cellulosic articles conventionally are hydrophilic in nature due to hydroxyl groups, which interact well with water. However, as sources for common wood fibers dwindle, alternative wood sources are being considered. In certain countries, such as Malaysia, the government has emphasized the use of alternate plantation-based, fast-growing tree species as wood fiber sources. Some alternate wood fiber sources, possessing relatively high content of extractive, may be less desirable due to lipophilic (hydrophobic) components, such as pitch, fatty acid, glycerides and di/triglycerides, steryl esters, alkanol esters, wax, sterols, terpene alcohols, etc., in their fibers. For example, Acacia is an alternate wood fiber source. Acacia wood fiber has been undesirable for use in making consolidated cellulosic articles due to its high content of lipophilic components, which interfere with the efficacy of typical formaldehyde binders. Applicant has discovered that lipophilic-containing wood fibers, such as Acacia fibers, are not compatible with commonly used binders in a typical blowline resination process for thin MDF door skins, sometimes resulting in poor processing, such as by having a high mass spring back of the fiber mat, fiber mat cracking, poor surface quality, poor coatability, and/or poor glue adhesion.
Therefore, there remains a need to develop processes to enable the use of lipophilic-containing cellulosic fibers in the formation of consolidated cellulosic articles without decreasing mechanical properties.